Looking for Good Info On Fork Swap

[KXSmoker]

I don't own a KDX but I have a 2001 KX125 and from reading some the pages on this form it looks like right many people on the form have experience with fork swapping and was hoping I could get some good solid information.

Last week I made an impulse ebay buy of some 2013 KX250F Showa SFF forks, although in my excitement I had no idea what I was buying. All I knew were that they were Showa forks and they looks super cool! So now I'm on the long discovery process to figure out what I need to get these forks set up on the 2001 KX125.

The 2001 KX125 has 46mm KYB forks. The 2013 KX250F has 48mm Showa forks. Just from measuring the clamp areas with a micrometer and not even trying to shove the Showa's into the OEM 2001 clamps I could tell they probably weren't gong to work out. Obviously, the 2013 KX250F clamps will work for those forks and there's an abundance of them being sold on ebay. The thing is this though, I want to keep the original factory steering performance of the KX125 but I have no idea of the offset of the 2001 KX factory clamps for one thing. I've searched all over and I just can't find it. I have come to find that aftermarket clamps for the 2013 KX250F seem to all advertise that they have 23mm offset so I'm not sure I want to use the 2013 KX250F clamps on the 2001 KX. So to questions No. 1:

- The 2005 KX125 I feel like might have the same clamp offset as the 2001 KX125 but had 48mm forks like the Showa forks that I bought. However, the 2005 KX clamps were for KYB brand forks and the forks I bought were Showa 48mm forks, so.. that doesn't necessarily mean that the Showa 48mm's will fit the clamps on the 2005 KX that had the KYB 48mm forks. Forks are sized by the lower fork tube and not the upper fork tube where they're clamped. So even though the KYB's and Showa's are both labeled as 48mm forks I don't know if the clamps from a 2005 KX will work on the Showa 48mm upper fork tubes as different brand forks may have differently sculpted upper tubes even though the lower tubes are the same size.

- Additionally, the center fork clamp hole spacing may be different from the 2005 KX 125 to the 2013 KX250F which might give me a problem finding proper wheel spacers.

I guess the answer is to just use 2013 KX250F clamps and just use all 2013 KX250 front end stuff, hub (potentially) and wheel spacers, and maybe even the brake calipers, and most definitely the brake line. The thing is though, is the offset the same with those 2013 clamps as my 2001 clamps and will that give me the same tight turning radius that I like on the KX125? I'm picky. I like the way the 125 runs and handles.

- Steering stops: The steering stops from the 2005 KX125 clamps are likely to be in the same spot as the 2001 KX125 which would be great, but not the stops on the 2013 KX250F clamps. I have found a solution (sort of, they're out of stock) for the steering stops here at Trick Engineering with these steering stop adapters http://trickeng.com/product/kx125-250-s ... p-adapter/. I don't know if they even plan on making anymore of those adapters. I went to their facebook page and they had a post last year saying they just made a whole new batch of them but that was over a year ago.

So what's anybody's best advise? Will the 2005 KX125 clamps work with 2013 Showa forks? Or should I forget about it and go with the "known" that the 2013 clamps and all the accompanying front end stuff from the 2013 clamps will work. But one thing about that to. Would I have to press out the steering stem from my 2001 KX125 clamps and press it into the 2013 KX250 clamps? Are the steering stem lengths the same? I have a press and that shouldn't be a problem.

[Chuck78]

Don't forget that half of the offset is in the fork lugs, which could potentially be significantly different between the two forks, so the original triple clamps may not even be relevant. Try to get a good measurement from the center of the fork tube to the center of the axle clamp area and compare both of them.
The steering stems are either going to be the exact length or the newer Fork steering stem will be a few millimeters longer, but could potentially be very workable with a spacer. The bearing size should be identical.

Those are quite nice forks, they are the single sided forks where you have adjustable external preload on one side because there is one big heavy fork spring in that side only, with lubrication oil and bushings, and no spring in the other side other than valving parts, and you have all of your compression and rebound in the other side, this way there are less internal chamber seals to cause additional friction and fiction, and you don't have metal particles from the spring wearing on the inside of the fork, floating around in the side that handles the valving. The damping oil is still separate in that fork from the lubrication oil, even in the damping-only side.

There is less info on setting these things up as I believe Kawasaki was the only one that used them, primarily I believe the KX250F, as I believe the same years KX450 used KYB forks. Around 2019, they switched, the KX250F became just the KX250, & used KYB through 2024, and the 2019 KX450 switched to some incredible Showa 49mm Twin Chamber forks, with a conventional dual spring setup. In 2025+, BOTH the KX250 & KX450 use the Showa 49mm Twin Chamber forks.

[Chuck78]

I personally would just try out the donor model year triple clamps and see how it rides. You could potentially have a machinist bore out your triple clamps as long as it's not taking too much material out, but I am always hesitant for this because any slight error in setup will cause the forks to not be perfectly parallel to one another, which can cause stiction and potentially dangerous operation.

Try and use a straight edge and some basic math to determine your triple clamp offset, and then the slightly more difficult part, try and measure the fork lug offset. Often a speed square or some perfectly 90° object may be needed with having the forks laying on the bench and the axle lug nut surface perfectly parallel to the bench, plus measuring calipers, to measure the lug offset. When I said some basic math is required, you can't just eyeball the sensors, you really need to measure off of one side or the other and then add or subtract half of the diameter of the opening to get to the center more precisely. Same goes with both the triple clamps and the fork's lugs.

[KXSmoker]

I appreciate the replies. I definitely came to the right forum for my questions. The answer for what I need to do looks like what I pretty much already knew. I'll have to swap all the front end parts over from the donor bike to the KX125 to make it work out without a problem and I'll just have to disregard the offset and see how it rides if I want to use those forks. I'm still curious what the difference might be. It's weird how I can't find the factory information about the offset of the two bikes.